Electronic device responsive to variable electrical conductances and capacitances of material, such as moisture content in lignocellulose materials



Feb. 19,- 1957 J DALLAS 2,782,367

ELECTRoNIC DEVICE RESPONSIVE TO VARIABLE ELECTRICAL CONDUCTANCES AND CAPACITANCES OF MATERIAL, SUCH As MOISTURE CONTENT IN LIGNocELLULosE MATERIALS Flled Nov. 3. 1952 10 hee t l INVENTOR. JAMEfi E DAMAS A 7 TOENEYS' Feb. 19, 1957 J. E. DALLAS 2,782,367

ELECTRONIC DEVICE RESPONSIVE TO VARIABLE ELECTRICAL CONDUCTANCES AND CAPACITANCES OF MATERIAL, SUCH AS MOISTURE CONTENT IN LIGNOCELLULOSE MATERIALS Filed NOV. 3. 1952 10 Sheets-Sheet 2 VOLTAGE ZEEO 4.f A A Q 7 Q 9 .z. "VGLTAGE 7 VOLT/1 GE VOLTA 6 E VOLTAGE +VOLT4GE INVENTQR. i/AME 5 DAZAAS' Feb. 19, 1957 J. E. DALLAS 2,782,367

ELECTRONIC DEVICE RESPONSIVE TO VARIABLE ELECTRICAL CCNDUCTANCES AND CAPACITANCES OF MATERIAL, SUCH AS MOISTURE CONTENT IN LIGNOCELLULOSE MATERIALS Filed Nov. 3, 1952 10 Sheets-Sheet 3 VOLTAGE ZERO "VOLTAGE won/m5 V V 6 +VOLTAGE EEO VOLTAGE INVENTOR. L//-. ma DA 1. L A 5 Feb. 19, 1957 J. E. DALLAS 2,782,367

ELECTRONIC DEVICE RESPONSIVE TO VARIABLE ELECTRICAL CONDUCTANCES AND CAPACITANCES OF MATERIAL, SUCH As MOISTURE CONTENT IN LIGNOCELLULOSE MATERIALS Filed Nov. 3; 1952 10 Sheets-Sheet 4 INVENTOR. JAMES 5. DALZAS Feb. 19, 1957 J. E. DALLAS 2,782,367

ELECTRONIC DEVICE RESPONSIVE TO VARIABLE ELECTRICAL CONDUCTANCES AND CAPACITANCES OF MATERIAL, SUCH As MOISTURE CONTENT IN LIGNOCELLULOSE MATERIALS Filed Nov. 5, 1952 10 Sheets-Sheet 5 A TTOPA/EK? Feb. 19, 1957 J. E. DALLAS 2,782,367

ELECTRONIC DEVICE RESPONSIVE TO VARIABLE ELECTRICAL CONDUCTANCES AND CAPACITANCES OF MATERIAL, SUCH As MOISTURE CONTENT IN LIGNOCELLULOSE MATERIALS Filed Nov. 3, 1952 10 Sheets-Sheet 6 +V0LTAG -VOLTAGE +VOLTAOE 325 EEO N A A I 7- VOLTAGE V V +VOLTA6E ZERO z VOLTAGE C VCLE'S VOLTAGE VOLTAGE INVENTOR. JAMES E DALAA5 Feb. 19, 1957 DALLAS 2,782,367

ELECTRONIC DEVICE RESPONSIVE To VARIABLE ELECTRICAL CONDUCTANCES AND CAPACITANCES OF MATERIAL, SUCH AS MOISTURE CONTENT IN LIGNOCELLULOSE MATERIALS.

Filed NOV. 3, 1952 10 Sheets-Sheet 7 INVENTOR. JAMES DALLAS BY I 421/ f/ if 1957 J. E. DALLAS ELECTRONIC DEVICE RESPONSIVE TO VARIABLE ELECTRICAL CONDUCTANCES AND CAPACITANCES OF MATERIAL, SUCH As MOISTURE CONTENT IN LIGNOCELLULOSE MATERIALS l0 Sheets-Sheet 8 Filed Nov. 3; 1952 I/IIIJIIIIIII III 7 IN VEN TOR.

A TTOPA/A-V 9 7 t 6 e e m 8% S "r 7C I HS 2 mmCLm C s E 0 W 1 E L B A I R E DAL S SPONSIVE VA TANCES AND CAPACITANCES OF MATERIAL, SU STURE CONTENT IN LIGNOCELLULOSE MATERIA Feb. 19, 1957 J.

ELECTRONIC DEVICE RE CONDUC MOI Filed Nov. 3. 1952 INVENTOR. JAMS 44145 BY a; 1 %4 rroeA/ l0 Sheets-She et 10 J. E. DALLAS Feb. 19, 1957 ELECTRONIC DEVICE RESPONSIVE TO VARIABLE ELECTRICAL CONDUCTANCES AND CAPACITANCES 0F MATERIAL, SUCH AS MOISTURE CONTENT IN LIGNOCELLULOSE MATERIALS Filed Nov. 3, 1952 United States Patent ELECTRONIC DEVICE RESPONSIVE TO VARIABLE ELECTRICAL QONDUCTANCES' AND CAPACI- TANCES 0F MATERIAL, SUCH AS MOISTURE CONTENT IN LIGNOCELLULOSE MATERIALS James E. Dallas, Seattie, Wash, assignor to Plywood Research Foundation, Tacoma, Wash., a corporation of Washington Application November 3, 1952, Serial No. 318,424

9 Claims. (Cl. 324-61) My invention relates to electric apparatus to determine or measure the electrical capacitative and conductive characteristics of material.

More particularly, it is an object of my invention to provide electrical apparatus to determine moisture levels of: various types of material or to provide apparatus responsive to predetermined moisture levels of materials.

This is a continuation-in-part of my co-pending application, Serial Number 218,343, filed March 30, 1951, now abandoned, for Electronic Device Responsive to Variable Electrical Conductances and Capacitances of Material, Such as Moisture Content in Lignocellulose Materials.

in fabricating plywood, moisture or water over a predetermined minirnum must not be present for best results in curing the adhesive. The total moisture content includes that in the sheets of veneer as well as the moisture added with the adhesive. If this varies over predetermined maximum levels, a poor bond obtains under commercial operating standards. It is an object of my invention to provide moisture responsive means operable on traveling veneer sheets to mark, sort or otherwise indicate the moisture level thereof.

If pieces of wood of unequal moisture content are employed in the fabricating of furniture, as table tops, then upon drying of the unalike pieces, warping and the like obtains and pieces of furniture are ruined because pieces of wood stock having unequal moisture content were employed in fabricating. My invention provides for determining the moisture level of pieces of wood stock in an in-line production process.

In the hardboard art, where comminuted pieces of lignocellulose or fibers are first formed and then are consolidated by an adhesive, such as a thermoset-phenolic resin, the total moisture content employed in the adhesive comprises both the moisture content of the pieces as Well as the moisture content added with the adhesive. Here again if the moisture content is not controlled within predetermined limits, there is poor adhesion and the hardboards are not adequate and may be adversely affected, as by steam action, as they are removed from the hot presses.

These and many others indicate the need of an accurate moisture meter or a device which is responsive and indicates moisture contents over or under predetermined levels and which will operate on materials moving on conveyors on in-line production.

Devices embodying my invention may be utilized to be responsive to moisture which is in solid materials, such :as lumber, veneer stock, plywood, paper, and other organic materials. Also, such devices may be used on granular or relatively finely divided materials, such as pieces of wood and wood fibers and non-aqueous liquids including therein dispersed moisture, such as particles of water dispersed in a hydrocarbon oil, as the continuous phase.

It is an object of my invention to provide an electronic device which will provide a signal which is proportional 2,782,367 Patented Feb. 19, 1957 "ice to the conductance and capacity reactances of a circuit including therein the particular material being tested or under observation. I

It is a further object of my invention to provide an electronic device and a circuit wherein the conductive and capacitative reactions of the material being tested provide a desired signal which may be utilized by a voltage responsive device. F

It is a further object of my invention to provide a device wherein there is the phase shifting of the electrical energy in a circuit of an electronic device andwhich phase shifting is responsive to the conductive and capacitative reactions of the material being tested. i

Prior art electronic moisture responsive devices generally employed an oscillating circuit and with wave lengths in the radio frequency range. A shortcoming of such devices was that the response signal tended to adversely follow variables, such as the air humidity conditions, and did not closely follow changes in moisture content of the material being tested and thus the instruments were not reliable under commercial operating conditions. Thus, in many instances the devices were of a laboratory character.

It is a further object of my invention to provide an electronic circuit wherein multi-element tubes are provided so that we have two tube sections each having at least a cathode, grid, and plate. Next, in such circuit I employ alternating currents out of phase with each other in the cathode-plate potentials of two tubes or two tube sections and employ a third alternating current out of phase with the other two in the grid circuits of the tubes. In such grid circuit, I cause a change of phase due to the conductance and capacity which is caused by the material being tested so as to obtain a voltage response signal between the cathodes of the said electronic tubes.

Other objects and advantages of the invention will become apparent as the description of the same proceeds and the invention will be best understood from a consideration of the following detailed description taken in connection with the accompanying drawings forming a part of the specification, with the understanding, however, that the invention is not to be limited to the exact details of construction shown and described since obvious modifications will occur to a person skilled in this art.

Figure 1 is a somewhat schematic wiring diagram illustrating one embodiment of my invention;

Figs. 2, 3, and 4 are schematic diagrams illustrating voltage curves and energy flow which may obtain in electronic tubes illustrated in Fig. l of the drawings;

Fig. 5 is a somewhat schematic wiring diagram illustrating another embodiment of my invention;

Fig. 6 is a somewhat schematic wiring diagram illustrating another form of my invention; 2

Figs. 7 and 8 are schematic views illustrating voltage curves and energy flow which may occur in two tubes of the circuit illustrated in Fig. 6 of the drawings;

Fig. 9 is a fragmentary perspective view illustrating a manner of utilizing the signal, responsive to the conduct-ance and capacitativo reaction of the material being tested, obtaining by reason of the previously mentioned circuits;

Fig. 10 is a perspective fragmentary view showing an alternative construction to Fig. 9;

Fig. 11 is a perspective fragmentary view showing a construction wherein the material being tested is in the nature of plywood or other sheet material;

'Fig. 12 is a fragmentary sectional and elevational view taken substantially on broken line 12 -12 of :Fig'. ll;

Fig. 13 is a fragmentary perspective view of still further modified form of utilizing a signal obtaining as described in connection with Fig. 9; p

Fig; 14 is a bottom plan view of a'still further modified form of device which may be utilized in connection with my invention, the same being particularly designed for use in connection with lumber but its utility is not limited to such use;

Fig. is a sectional view of the structure shown in Fig. 14 and taken substantially on broken line 1S15 of Fig. 14, and there is further shown a fragment of a piece of lumber stock in side elevation and a fragment of a bed for supporting said lumber stock;

Fig. 16 is a fragmentary perspective View of a still further modified form of device which may be utilized in connection with my invention, the same being particularly designed for use in connection with veneer stock, as wood veneer stock, but its utility is not limited to such use;

Fig. 17 is a fragmentary sectional view taken substantially on broken line 17*17 of Fig. 16 and showing in addition a fragment of a piece of veneer stock passing over the said device of Fig. 16 and also showing holddown means to maintain the plywood in close relation to the electrodes;

Fig. 18 is a fragmentary perspective view of a still further modified form of a device which may be utilized in connection with my invention, the same being particularly designed for use in connection with paper stock, but its utility is not limited to such use;

Fig. 19 is an elevational view taken substantially on broken line 19-19 of Fig. 18;

Fig. 20 is an elevational view taken substantially in the direction of broken line 20-20 of Fig. 18; and

Fig. 21 is a view similar to Fig. 1 of a modified wiring diagram illustrating another embodiment of my invention.

Referring now to Fig. 1 of the drawings, conductors 20 and 21 represent a source of electrical energy. It is desirable that the energy on such conductors range between and 15,000 cycles per second so as to be within the complete audio frequency range (see The Radio Amateurs Handbook, 28th edition, 1951, page 20). It is a characteristic of my invention that the energy between the condenser through which the material passes and is tested be in a circuit wherein 15 to 15,000 cycles per second energy is passing. This is to be distinguished from circuits employed in moisture meters of the prior art wherein oscillating circuits were employed. Such circuits generally employed energy across the condenser where the material was being tested in the radio frequency range, such as over 15,000 and generally in practice of about 10,000,000 cycles. Where the electric energy was in the radio frequency range, the

devices were adversely affected by many conditions, such 1 as changes in weather or in changes of moisture content of the air. Where frequencies in the audio range are employed, as in my invention, the readings and performance tend to closely follow only changes in the dielectric character of the material being tested or otherwise checked.

Preferably a pilot light 22, which is illustrated by way of example as being of the glow discharge type, is employed to visually indicate that electrical energy is on conductors 20 and 21. Also the electrical energy on conductors 20 and 21 may be of the usual voltage commonly found around any industrial plants, that is, between 115 and 550 volts A. C.

Switches 23 and fuses 24 are employed for their usual purposes. Also preferably a pilot light 25 is employed for visually indicating that the switches 23 and fuses 24 are in operating condition.

An input current from conductors 26 and 27 travels to the voltage regulator indicated generally by 28. Preferably the voltage regulator 28 includes therein an oscillator or other means to provide a regulated secondary voltage on conductors 29 and 30 which has generally a square-top wave. Also the voltage regulator 28 maintains a constant voltage, such as 115 volts, so long as there is a substantially uniform load-the structure of my invention illustrated in Fig. 1 provides a substantially uniform load.

The secondary voltage along conductors 29 and 30 is delivered to an isolating transformer 31 which preferably has a 1 to 1 ratio. The secondary voltage from isolating transformer 31 is delivered to variable transformer 32. By the use of variable transformer 32 any desired secondary voltage may be delivered to conductors 33 and 34. To obtain different characteristics and for different uses of my invention, it may be desired to raise or lower the voltage on conductors 33 and 34. The variable transformer 32 preferably has a fine adjustment so that increments of approximately half a volt may be obtained. In other words, any voltage between zero and the output capacity of the transformer 32 can be obtained with a relatively small unit variation.

Preferably a volt meter 35 as well as a pilot light 36 are coupled between conductors 33 and 34 for obvious purposes. Also fuses 37 and switches 38 may be employed. Transformers 39, 40, 41 and 42 are fed by the energy from the secondary of transformer 32 which passes along conductors 33 and 34. Polarity dots are shown in connection with transformers 39, 40, and 41 to indicate like instantaneous polarity. The transformers 39 to 41 inclusive are step-up transformers and in the particular installation of Fig. l have a ratio of about l to 2 /2. Transformer 42 is a step-down transformer with a tapped secondary. Transformers 39, 40 and 41 are employed to obtain a voltage of approximately 270 volts to the plates of electronic tubes 43 and 44. Transformer 42 is utilized to energize the filaments of the electronic tubes 43 and 44. As illustrative of electronic tubes which may be employed in my invention, I have illustrated tubes 43 and 44 as 6SL7GT. The filaments of such tubes may be heated and 5 to 6.3 volts may be utilized for such purpose. Such tubes are dual triodes and I have shown both sections in parallel between the same wires and this provides for passage of more current and a more durable construction. Obviously, functionally two single triodes could be employed. 1 provide two variable resistances 45 and 46. The variable resistance 45 is connected with a common conductor 47 through a variable resistance 48 and the variable resistance 45 is connected by a conductor 49 with the variable resistance 46 and in turn the cathode of tube 44. As the cathodes 50 of tube 43 and the cathodes 51 of tube 44 each go to the common conductor 47 through a portion of variable resistance 45 and variable resistance 48, an adjustment of the variable resistance 45 functions to balance the cathodes of the tubes 43 and 44. Preferably the adjustment of the variable resistance 45 is rather coarse and then a fine adjustment can be obtained through the variable resistance 46. Thus the resistance of variable resistance 45 may be in the order of ten times that of variable resistance 46 for practical results. The conductor 47 connects to the various transformers 39, 40, 41, and 42 by conductors 52, 53 and 54 respectively.

The secondary of transformer 40 impresses a voltage on the plates 5'5 of tube 43 by way of conductor 56. The secondary of transformer 41 impresses the voltage on the plates 57 of tube 44 by way of conductor 58. The transformers 40 and 41 are each shown as having their primary and secondary windings wrapped in the same direction. With such an arrangement and with the common wire 53 connected to opposite ends of the secondaries and with the conductors 5'6 and 53 connected to opposite ends of the secondaries of said transformers 40 and 41, the voltage impressed on the plates 55 of tube 43 will be degrees out of phase with the voltage impressed on the plates 57 of tube 44. Obviously it is possible to reverse the winding of transformers 40 and 41 as respects each other, or one winding of a single transformer as respects the other, and it is well within the skill of those in this art to obtain similar results to those just described by employing such procedures, Other phase shift mechanisms may be employed rather than the combination illustrated by transformers 40 and 41. Also the phase shift need not be 180 degrees although I preferably desire such phase shift when single phase current is employed.

When tube 43 operates, energy passes from one end of the secondary of transformer 40 along conductors 53 and 47, through variable resistance 48, through a portion of adjustable resistance .5, from cathodes 5G to plates 55, and thence along conductor 56 to the other end of the secondary of transformer 40. At the same time when tube 44- is operating, energy passes from conductor 53 which is one end of transformer 41 along conductors 53 and 47, through adjustable resistance 48, through the lower portion of adjustable resistance 45, along conductor 49, through adjustable resistance 46, from cathodes 51 to plates 57, and thence by a conductor 55 to the other end of the secondary of transformer 41. As each tube is operating, the energy thus passes through variable resistance 48 and any adjustment of such variable re sistance will thus determine the flow of energy from the cathodes of the tubes to the plates. It will also control the grid bias level of the tubes 43 and 44 which in turn affects the sensitivity of the entire circuit.

The common conductor 47 is preferably connected with the grids 63 and 64 through variable resistance 47' which is one way of imposing a desired potential on the grids of the electronic tubes. This, per se, is in accordance with established practice, and other established practices of maintaining a desired voltage level on the grids of electronic tubes, as the grids of tubes 63 and 64, may be employed. Such common practices include the use of batteries in series with a variable resistance similar to the resistance 47.

The filaments Su and 60 of the tubes 43 and 44 are energized by the secondary of transformer 42 as previously stated. Transformer 42 preferably has a center tap which is connected with conductor 54 which in turn is connected with the common conductor 47. The energy from the secondary of transformer 42 is connected with conductors 61 and 62 which are connected with filaments 59 and 60.

The grids 63 and 64 of tubes 43 and 44 are preferably energized by energy which is out of phase with the energy from either the secondary of transformer 4% or the secondary of transformer 41. This may be accomplished by the circuit employing transformer 39. One end of the secondary of transformer 39 is coupled by a conductor 65 with an inductor 66. inductor 66 is coupled to variable resistance 67 which in turn is coupled to inductor 68. Inductor 68 is coupled by conductor 69 with potentiometer 70. Potentiometer 70 is connected with fixed resistance 71. Energy from fixed resistance 71 passes via the conductor 72. to the other end of the secondary of transformer 39. Condenser 73 is disposed between conductors "72 and 69. Conductor 52 is connected with the common conductor 47. Thus electrical energy can be picked up from the center arm of the potentiometer 70 which is out of phase with the energy from the secondary of transformers 4t and 41 which are also connected to the common conductor 47. By shifting the center arm of the potentiometer 7t) there is a change in the capacitative and conductive reaction of the energy on said center arm. A portion of this reaction is also a matter of phase shift and voltage change. While I have found that I may shift the phase of the energy on the center arm of the potentiometer 76 as respects the energy on conductors 56 and 53 approximately 120 degrees with the apparatus and circuit illustrated, Ipreferably initially shift the phase approximately 90 degrees for optimum results.

There are obviousiy many other ways to shift the phase of the energy on conductor 74 as respects the energy on conductors 56 and 58, audit is to be understood that the apparatus and circuit just described is illustrative rather than limiting.

From the foregoing it will be apparent that the energy in the secondary of transformers 40 and 41 as well as the energy passing on a center arm of potentiometer '70 are currents which are out of phase with each other and which have been obtained by known apparatus from single phase electrical current. Consequently, if polyphase current is available, such as three phase, the apparatus and wiring diagram as illustrated in connection with Fig. 6 of the drawings may be utilized. Thus, it is to be understood that my invention is not limited to the use of single phase electrical current as a source of supply.

The grid circuit includes the secondary of transformer 39, fixed resistance 66, variable resistance 67, inductance 63, condenser 73, potentiometer 70, and fixed resistance It. it is desirable that the grid circuit include capacitance, such as is provided by a suitable condenser 73. When suitable capacity and conductance reactions are provided in the grid circuit to provide for an initial phase shift, then the circuit is more sensitive to capacitance and conductance changes in the material condenser 75 and variation therein due to the capacitance and conductance of material passing between the plates of the material condenser '75. Once we provide a suitable capacity to condenser 73, then it is desirable to provide an inductive reactance in the circuit so that the circuit of Fig. 1 can approach resonance. If the inductive reactance and the capacitative reactance are equal, of course the circuit is resonant. As the circuit approaches resonance there will be a voltage increase in the circuit and by selection of appropriate sizes of resistances as Well as inductive and capacitative reactances, a suitable grid circuit may be provided. Thereafter by adjusting the center arm of the potentiometer 70 a suitable voltage may be impressed on conductor 74. Condenser 76 is merely a safety device to limit current passing to the plates of condenser 75. Depending upon the physical condition as well as the conductance and capacity of the material being tested and which passes between the plates of condenser 75, capacitative as well as conductive changes of the material are reflected to change the phase relation of the voltage impressed on the grids 63 and 64 relative to the plate voltages on the plates and 57. I have 'found that where the grid circuit has had its initial phase in part determined by a capacitative reactance in the circuit that the grid phase is more sensitive to change by the condition of material condenser 75 than when the grid phase is not so initially determined.

Condenser 75 represents the passageway through which the material being tested passes. As it appears herein it may be desirable to measure the capacity as well as the conductance of some types of material, or it may be desirable to actuate a relay when the electrical capacity and/ or conduction of the material reaches under or over a certain level. Thus it is to be understood that the material condenser 75 shown in Fig. 1 of the drawings is by way of illustration and not by way of limitation. For convenience of expression 75 will be referred to as the material condenser.

Energy from the center arm of the potentiometer passes via conductor 74 through condenser 76 along conductor 77 and through material condenser via conductor 78 to the grid 63 of tube 43. Also energy passes from condenser 75 to conductor '79 to the grid of tube 44.

The cathodes 50 of tube 43 are connected with conductor 80 and the cathodes 64 of tube 44 are connected with conductor 81. Conductors 80 and 81 are preferably interconnected through a condenser 82 disposed in conductor 83. Also, conductors S0 and 81 have connected therebetween voltage responsive devices, such as meters, lumber marking devices, sorter control mechanisms, and other devices which are desired to be operated when the capacity and conduction of the material being tested system provides the desired signal; Elsewhere herein I have indicated a number of illustrative devices which may provide or cause the signal obtaining between conductors 80 and 81, which signal bears a direct relationship to the capacity and conductance of the material which may be disposed between or pass through the material condenser 75.

Before discussing the illustrative mechanism shown in Fig. l of the drawings which is operated by the signal between conductors 8t) and 81, it is believed it will be useful to further discuss'the manner in which such signal is obtained. In obtaining a signal between conductors 80 and 81, adjustable resistors 48, and 46 are adjusted to provide a null-point or a condition of substantially no signal or voltage drop between conductors 80 and 81 and tubes 43 and 44 are in equilibrium or in balance.

The flow in the tubes 43 and 44 between the cathodes 50 and 51 and the plates 55 and 57 respectively depends upon the voltage values operating at the same time and imposed relatively on the cathodes, plates and grids. Thus, in determining the signal or differential in voltage between the conductors 80 and 81, it is necessary to determine the phase relationship between the voltage impressed on the grids and plates of the said tubes 43 and 44.

Referring now to Fi 2 of the drawings, the modified square curve 84 represents the voltage impressed on the plates 55 of the tube 43 while the modified square curve 85 represents the voltage impressed on the plates 57 of the tube 44. The modified square curve 86 represents the voltage impressed on the grids 63 and 64 of the tubes 43 and 44. In such graphical illustration the curve 85 lags the curve 84 by 180". Also, the curve 86 leads the curve 84 by 90. There has been no attempt to indicate in the curves of Figs. 2 to 4 actual amplitudes as curves 84, 85 and 86 represent voltage levels while 0 curves 87, 88, 89, 90, 91, and 92 represent energy flow, as voltage and amperes or fractions thereof. Thus, when the curve 84 is negative, energy may pass between the cathodes 50 and plates 55 of tube 43, providing, however, the grid 63 is more positive than the initially set cut-off point which is regulated by capacitors and resistances in the circuit. However, grid voltage, represented by curve 86, is out of phase, as indicated in Fig. 2, by 90 with the voltage impressed on the plates 55 which is represented by curve 84. Thus, we have a flow between the cathodes 50 and the plates 55 of tube 43 which is represented by the how curve 87.

Similarly, the grid bias or the voltage impressed on the grid 64 of tube 44 affects the flow between cathodes 51 and plates 57 and the flow in the tube 44 is represented by the curve 88. While the curve 88 lags curve 37, nevertheless, the values are substantially the same and thus, the flow along conductors 80 and 81 is substantially the same.

Referring now to Fig. 3 of the drawings, the curve 86 has been shifted 45 so that it leads curve 84 by such amount. The curve 86 may be shifted by changes in the conductance and capacity of the material passing between the plates of material condenser 75. The amount of shifting of the phase will depend upon the characteristics of the material passing between the plates of said condenser 75. By way of illustration in Fig. 3 it is assumed that the material present between the plates of condenser through its capacity and conductance has shifted the phase of the voltage delivered to conductor 79 by 45 or. in other words, has shifted curve 86 by 45 as is illustrated in Fig. 3, so that said curve 86 leads curve 84 by 45 rather than 90. With such shift the positive values of the voltage curve 86 are operating at a time to be more etfectivc relative to the curve 84 and relative to the bias value in time intervals of the grid 63 and hence the energy passing between the cathodes 50 and the plates 55 is represented by the curve 89 of Fig. 3, Whereas the energy passing between the cathodes 51 and the plates 57 of tube 44 is represented by the curve 90. The relative values of the energy passing represented by the curve 89 and the curve 90 will illustrate the value of voltages present on the conductors 80 and 81. Due to the relatively high value of the curve 89 relative to the curve 90, a very substantial differential in voltage appears between the conductors 80 and 81 which may be utilized as a signal to operate various devices and thus be responsive to the capacity and conductance of any material disposed between the plates of condenser 75. If desired, instruments may be utilized to measure the differential and such differential will be proportionate to the conductance and capacity of the material disposed between the plates of material condenser 75, or, if desired, relay or electronic means may be employed to operate when the differential reaches a certain value.

As indicated in Figs. 2 and 3, the initial phase relation and the phase shift is designated to increase the value of curve 89 as respects curve 90. However, the initial phase relation of curve 86 may lag curve 85 by and thus any shift of phase of the curve 86 will tend to increase the value of curve 88 relative to curve 87. This may be provided by apparatus wherein the phase shift possible by the circuit including potentiometer 70, or other phase shift apparatus, is such so that initial setting may be made so that the curve 86 indicating the voltage in the grid circuit lags the voltage represented by curve 84 by a desired number of degrees, such as 90, rather than leads the same. if the voltages impressed on the plates 55 and 57 are out of phase with each other by 180, then if the grid voltage is relatively out of phase with the voltages represented by curves 84 and 35 by 90, we will have a null-point or a point wherein the grid voltage represented by curve 86 similarly affects the flow in both tubes. Any variation from such null-point will cause more flow in one tube than in the other and thus provide a relative differential in the flow on conductors 80 and 81 which can be used as a signal to operate suitable devices.

Referring now to Fig. 4 of the drawings, the curve 86 has been shifted to be in phase with curve 84 and 180 out of phase with curve 85. This phase shift is due to the original setting plus a shift due to the material present between the plates of condenser '75. Thus there is no energy flow in tube 44 (represented by curve 92) and maximum flow in tube 43 (represented by curve 91) and thus maximum signal between conductors 84) and 81 obtains. This may be accomplished by selecting a suitable initial phase relation between the voltages on plates 55 and 57 and on grids 63 and 64 so that maximum shift of grid voltage phase within the limits of the grid circuit and of material condenser 75 will bring such results.

In Figs. 2, 3, and 4 of the drawings, I have shown modified square top curves. Such energy is provided by reason of voltage regulator 28 and provides for a more desirable signal voltage between conductors 89 and 81 than the common sine wave curve. However, it is to be expressly understood that voltage having a normal sine curve can be provided by voltage regulator 28 and the curve thereof will be reflected in the voltages from transformers 39, 4t 41 and 42.

Referring again to Fig. 1 of the drawings there is shown an illustrative way in which the signal between conductors 80 and 81 may be utilized by a voltage responsive device. Such a device is responsive to voltage changes even though there is relatively low current or amperage flowing and relatively negligible variations in the current flow. Thus, by way of illustration, energy from voltage regulator 28 is delivered to conductors 93 and 94. A relay indicated generally by 95 has its switch mechanism disposed between conductors 93 and 96. Thus, whenever the switch mechanism of relay 95 is closed condoctors 93 and 96 will be interconnected. Relay 97 has its coil connected with conductors 96 and 98. Condoctor 98 is connected with conductor 94. Thus, wheneverrelay 95 hasits switch mechanism closed, the coil of relay 97 will be connected between conductors 93 and 94. v

Energy from conductor 3'1 connects with conductor 99, along conductor 100, through the switch mechanism of relay 101, along conductor 102, through the armature of solenoid 103 of resetting relay 111, along conductor 104, along conductors 105 and 106, through the switch blade of marker mechanism 107, along conductor 100, and along conductor 109 to the other conductor or source of energy 93. Thus, if the marker mechanism 107 has its switch mechanism in closed position, and if the switch mechanism of relay 101 is in closed position, and if the switch mechanism of relay 101 of the timer integrator 110 is closed, the solenoid 103 will be energized and open the switch points of latching relay 111. The timing integrator 110 utilizes relay 101 therein and the switch points of said relay 101 are held open for time periods of predetermined l ngths which are intermittent and start each time the marker mechanism 107 operates.

Thus, if a marking device 107 is employed to mark material, as lumber, passing between the plates of condenser 75, the marking device of said marking mechanism 107 can be timed to operate only at predetermined timed intervals. Thus, if traveling lumber passes between the plates of condenser 75 it will be possible to limit the minimum spacing between marks to a practical level depending on time and rate of travel. In a practical demonstration where thirty-six inch long boards were permitted to travel between the plates of condenser 75, I arbitrarily chose a minimum spacing between marks of twelve inches-each mark being made only when a signal of appropriate value was present between conductors S and 81.

Whenever the material present between the plates of condenser 75 has a capacity and conductance of a predetermined level, then a signal is provided between conductors S0 and 81. Commencing with conductor 80, conductor 112 connects the same with a filtering system, as an inductance 113. Inductance 113 is connected by conductor 115 with the coil of the relay 114 of the latch relay 111 and by conductor 116 to conductor 81. In order to control sensitivity, a conductor 117 is provided connecting conductor 115 with either of two selected adjustable resistances 118 which are in turn coupled with conductor 81. Thus, whenever a signal over predetermined value is passing between conductors 80 and 81, the relay 114 will tend to close the switch mechanism of the latch relay 111. However, if the solenoid 103 of the latch mechanism is energized, it will prevent closing of the switch mechanism of the latch relay 111.

Conductor 94 is connected with conductor 99 which in turn is connected by conductor 100 with the switch mechanism of relay 101 of timer integrator 110. Energy from relay 101 passes along conductor 102 to the coil of relay 120, thence along conductor 121 to conductor 106, thence through the blades of the switch mechanism of marker mechanism 107, thence along conductors 108 and 109 to the other source of energy 93. Thus, if the switch blades of marker mechanism are closed and if the switch blades of relay 101 of timer integrator 110 are also closed, the switch mechanism of relay 120 will be closed. Upon closing of said switch blades of relay 120 two circuits will be established. One circuit thereof is an electrical holding circuit and comprises conductor 122 connected with conductor 93, as by conductors 108 and 109, and the other end portion of said conductor 122 connects with conductor 105 through the upper switch of the switch mechanism of relay 120. Thence energy passes along conductors 105 and 121, through the coil of relay 120, thence along conductor 102, thence through the switch mechanism of relay 101, thence along conductors 100 and 99 to conductor 94 which is the other conductor of the source of electrical energy. The holding circuit so described remains energized once it is energized so long as the switch mechanism of relay 101 is closed. I I

The timer integrator 110 is provided with a reset means or starting interval which is accomplished by energizing the coil of relay 120. Suitable mechanism is provided in the timer integrator 110 to close the switch of relay 101 for a predetermined period and the circuit thereof includes conductors 123 and 124 which are electrically interconnected by the lower switch blade of switch blade mechanism of relay 120. Thus the start of the predetermined period is responsive to relay 120. Suitable power for the timer integrator 110 may be obtained from conductors 125 and 126 which are respectively connected to the conductors 94 and 93-conductor 125 being connected by conductor 99 with conductor 94 and conductor 126 being connected with conductor 93 by conductor 109.

I have shown a D. C. relay 95 which is operable by a source of rectified A. C. represented by conductors 127 and 128. My rectifying apparatus is indicated generally by 129t-he input energy being obtained from conductors 93 and 94. The relay 95 has its coil connected to conductors 12S and 134, thence through the switch rnechanism of latch relay 111 and thence to conductor 127. Thus, whenever relay 114 closes its switch mechanism in response to a signal of a predetermined value between conductors 80 and 01 (due to the capacity and conductance of material between the blades of condenser relay 95 will close. Closing of relay 95 permits a circuit to be completed through coil of relay 97 and through the timer mechanism at predetermined periods of time. Whenever the circuit may be completed and there is the desired impulse between conductors and 01, relay 111 closes closing relay which in turn closes relay 97 and the marking device 107 is operated and relay closes. The holding circuit described in connection with the upper switch blade of relay 120 causes relay 120 to remain closed until the relay 101 opens. The opening of relay 101 is in response to the time mechanism in the timer integrator 110. Whenever relay 97 closes it establishes a circuit to the solenoid of marker mechanism 107. This circuit may comprise conductors 130 and 131 connected respectively to conductors 21 and 20. The switch mechanism of relay 97 is connected in the ciruit with solenoid 132 of the marker mechanism 107. The marker mechanism may be a spring loaded marking device which operates to mark material with a suitable indicia, such as a chalk mark, the marker is; illustrated generally by the pointer 133. As a matter of good wiring practice, I have isolated the circuit op erating the solenoid 132 of the marker mechanism 107' from the other control circuits. Similarly, I have isolated the energy flowing between conductors 80 and 81 from the circuit including relay 95.

Obviously, other types of controls or electrical hookups may be employed other than those described in connection with the drawing of Fig. 1 and in Fig. 1, I have merely attempted to set forth a suitable manner of utilizing the impulse between the conductors S0 and 81.

The various transformers, condensers, potentiometers, tubes, and other devices indicated in Fig. l of the draw ings have to be selected to have relative electrical values to provide for an operative circuit. As such are known to those skilled in this art it will be understood that the various parts will be selected as to values in accordance with good electronic practices. The voltage across the material condenser '75 may have various values. The voltage value, of course, will depend upon the gap between the plates of material condenser 75, and the size or" the plates, as well as the capacitative and conductive reactances of the material being tested or checked. In an example where pieces of wood of substantially threequarters of an inch in thickness were passed between spaced electrodes which were spaced approximately an inch apart, 1 selected the parts and arranged for approxi mately volt drop between the two plates of the material condenser 75.. However, on test machines I have had good results with voltages as low as 50 volts drop across plates of the material condenser. Generally, voltages in the nature of 300 to 1000 volts are desirable, where there is approximately a one inch gap between the plates of material condenser and the material being tested is or" a lignocellulose character, to give desired sensitivity.

Referring now to a modified form of my invention illustrated in Fig. 5, some of the primary changes are to provide electronic means having a function of providing a voltage to the plate of one of the electronic tubes which is out of phase, such as 180, with the plate of another tube. Thus, in the illustration of Fig. 5, the voltage on the cathode plate system of one tube is 180 out of phase With that of the cathode plate system of the other tube. Another substantial change, indicated by Fig. 5 of the drawings, is to provide by electronic means a third voltage to the grids of both said tubes which is initially out of phase with that of the cathode plate system of the said two tubes and to accomplish the same by electronic tubes and circuits.

in Fig. 5 of the drawings, schematically represents a source of a plurality of electrical energies. The energy on conductors 136 may be A. C. of suitable strength to feed transformer 137. Transformer 137 preferably has a pturality of secondaries to furnish a voltage of desired strength between conductors x and y; another voltage of desirable strength between conductors l and m and still a third voltage between conductors 0 and p. The voltages so obtained are utilized to heat the filaments of the various electronic tubes shown. Thus, if desired, iso lated sources of electrical energy for heating the filaments of the tubes may be obtained. the illustrations of the circuits as clear as possible, the complete circuits to the various tubes are not illustrated as ob iously to complete the circuits will be well Within the knowledge of those skilled in this art.

The conductors 138, 139 and 141) respectively represent energy having the characteristics of that obtained from one end, the center tap, and the other end of a secondary of a transformer. Conductors 141 and 142 represent a source of D. C. and the conductor 1 12 is interconnected with the conductor 139 to provide the common wire of the system. The common conductor 139 is connected with conductor 143, adjustable resistor 144, and thence by conductor 145 to the cathodes of the electronic tubes 146 and 147. As an example, tubes 146 and 147 may be a common type, such as 6L 807, etc. grid of tube 146 is fed by conductor 13S, conductor 148, through coupling condenser 149, and conductor 151 The grid of tube 147 is fed by conductor 140 through coupling condenser 151 and along conductor 152 to the grid of said tube. Grid returns for the grids of tubes 146 and 147 is provided through variable resistances 152. This portion of the circuit described has somewhat similar characteristics to a push-pull circuit wherein the grids of two triodes are connected to opposite ends of the secondary of transformer, and the center tap of the transformer is connected to the cathodes of said tubes. Thus, the voltages obtaining on the plates of the tubes 146 and 147 will be 180 out of phase with each other. To the plate of tube 146 is applied a D. C. potential from conductor 141 and through fixed resistance 153. Tl e same D. C. potential is applied to the plate of tube 147 from conductor 141, along conductor 154, and through fixed resistance 155 and thence to the plate of tube 14-7. Energy flowing between the cathode and the plate ct tube 147 will thus flow between common conductor 156 and conductor 157, while energy flowing between the cathode and the plate of tube 146 will flow between condnctors 156 and 158. Isolating and coupling condensers 1:39 are disposed in conductor 156. Fixed resistance 160 is disposed between the common conductor In order to keep The 156 and the conductor 158 and fixed resistance 161 is disposed between the common conductor 156 and conductor 157. The conductors 15S and 157 respectively feed the plates of tubes 162 and 163. The cathodes of tubes 162 and 163 are fed from the common conductor Also, the tubes 162 and 163 should be caused to balance and have a common flow if similar impulses are connected with their grids. Thus, I provide a variable resistance 164 coupled to the center leg of a potentiom eter 165. The potentiometer 165 provides for a coarse adjustment while the variable resistor 166 provides for a finer adjustment. The output of the variable resistor 166 is connected with the cathode of tube 162 while the output of the other leg of the potentiometer 165 is connected to the cathode of tube 163 via conductor 167.

A D. C. voltage is imposed on the grids of the tubes 162 and 163 and this may be accomplished by connecting the common conductor 156 with a source of direct current 163, which may include a battery. A potentiometer 169 is employed between the source of D. C. 168 and conductor 170, which conductor 170 is in turn connected to each of the grids of the tubes. Thus, suitable bias may be provided between the common conductor 156 and the grid of each of tubes 162 and 163.

The conductors 171 and 172 are functionally the same conductors as 86 and 81 of the form of my invention illustrated in Fig. 1. As any response by the said conductors can be used in the manner described in connection with Fig. 1, I have merely indicated in Fig. 5 a condenser 173 disposed between said conductors 171 and 172 and have diagrammatically indicated a voltage responsive device, indicated generally by 174, which is coupled between the cathodes of tubes 162 and 163. The tubes 162 and 163 correspond with the tubes 43 and 44 of Fig. l and the voltage operating between the cathode and plate of tube 162 is 180 out of phase with the voltage disposed on the cathode and plate of tube 163. Again 1 dispose the A. C. voltage on the grids of the tubes out of phase with either of the voltages in the cathode plate combination of either tube. Again preferably I provide for an initial 90 out of phase of the A. C. grid voltage as respects the cathode plate voltage of the said tubes 162 and 163. Thereafter, any shift in the phase of the grid voltage causes more energy to flow in one tube than in the other and thus gives me the signal between conductors 171 and 172. For convenience of illustration I have shown tubes 146, 147, 162, 163, and 175 as single section triodes.

In connection with Fig. l of the drawings, 1 provided transformer 39 and inductor 68 operating in a suitable circuit to provide grid voltage in the desired out of phase relationship as respects the cathode-plate voltages of the two tubes. Such type of circuit, illustrated in Fig. 1, requires a circuit somewhat in resonance in order to get proper voltage rise. If it is desired to not obtain the desired voltage by such a system, I can employ alternately either in Fig. 1 or as illustrated in Fig. 5 one means to shift the phase of the grid voltage and other means to amplify the voltage value.

This may be acomplished by utilizing any suitable source of A. C. energy, such as that represented by the conductors 138 and 139. Inductor 176 is disposed in conductor 139 and connected with coupling condenser 177. Coupling condenser 177 is in turn connected with a conductor .3715. r; plurality of variable resistances 179, each having a different value, are provided in parallel. A plurality of condensers 180, each having difiierent values, are disposed in parallel. The condensers 180 are coupled by conductor 181 and coupling condenser 182 with conductor 138. A movable contactor arm comprising independently movable portions 183 and 183 bridges between any one of the variable resistances 179 and any one of the condensers 180. The output conductor 184- thus provides a voltage as respects the common conductor 139 which has been assess? shifted a desired amount relative to the cathode-plate voltages of the tubes 162 and 163. As indicated in connection with Fig. 1, it is a matter of selecting appropriate capacitative-and conductive reactances as well as resistance to tune a circuit or provide a resonant circuit. With a resonant circuit of course, the voltage may in crease tremendously and the voltage on conductor 184 might be used similar to the manner described for the use of conductor 74 of Fig. 1. However, as a modification and further illustration of my invention to indicate that resonant circuits are not necessary, I show the conductor 184 connected to a potentiometer 185 which in turn is connected with conductor 139. The center leg of the potentiometer 185 is connected to the grid of tube 175. The cathode of tube 175 is connected with conductor 139 through a variable resistance 186 paralleled with a by-pass condenser 187 to conductor 188 which is connected with conductor 139. The plate of tube 175 is connected with conductor 189. Conductor 189 functions the same as conductor 74 of Fig. 1 and has disposed therein a coupling condenser 76 and the material condenser 75. In view of the fact that these parts may be identical and have similar functions they are given the same numbers. The material condenser 75 is connected by conductor 190 with a D. C. blocking condenser 191 (D. C. from source 168 was imposed on conductor 170). Alternating current energy from conductor 190 is imposed on conductors 170 and in turn with the grids of the tubes 162 and 163. By the use of tube 175 a voltage of a desired level may be imposed on the grids of tubes 162 and 163 and the phase shift of said voltage may be determined in a non-resonant circuit as has just been described. D. C. voltage may be impressed on the plate of tube 175 by any suitable means, such as conductor 192 connected with one source of D. C. through conductor 154. Energy from conductor 192 passes to inductor 193, to variable resistor 194 and thence to the plate of tube 175. Blocking and filtering condensers 195 are disposed between conductors 192 and 139 to a suitable filtering network back to the common 139.

Referring now to Fig. 6 of the drawings, an embodi ment of my invention employing polyphase, as threephase A. C., is illustrated. The source of polyphase energy is indicated by the box 196 shown by dash lines in said Fig. 6. As indicating a suitable source of threephase A. C., the secondary of a star connected transformer is shown. In a star connection, the three secondary windings have a common source conductor 197. The other end of the secondaries are respectively source conductors 198, 199 and 200. Thus, the source conductors 198, 199 and 200 represent the three legs of a source of three-phase A. C. and source conductor 197 represents the common of a star connected three-phase secondary.

In said Fig. 6, I preferably employ a non-resonant circuit and thus by electronic means provide suitable voltage to the material condenser 75 somewhat similar to the circuit illustrated in connection with Fig. 5 for the same purpose. -Thus, sourceconductor 198 is con nected through coupling condenser 201 with conductor 202. Similarly, source conductor 199 is connected with conductor 203 through coupling condenser 204. The conductors 202 and 203 are connected respectively with conductor 197 through fixed resistances 205 and 206.

As any ofthe circuits embodying my invention may employ pent'ode tubes, or other. multi-element tubes, and obtain the inherent advantages of such types of tubes, 1 have thus shown pentode tubes 207 and 208 in a portion of the circuit of Fig. 6 to illustrate such usage. The conductors 202 and 203 are connected respectively with the grids 209 and 210 of the tubes 207 and 208.

The box 211 represents a source of single phase A. C. and two sources of D. C. having appropriate values.

shown the filament circuits to the electronic tubes of Fig. 6 nor appropriate fuses and switches as fuinising the same is well within the knowledge of those skilled The conductor 212 may be the positive in this art. leg of a source of D. C., such as 500 or 600 volts. Conductor 213 will be the negative leg of such source of D. C. Also, conductor 213 is a common wire and also the negative of a second source of D. C. represented by the conductors 214 and 213. The latter source of D. C. represented by conductors 213 and 214 may have a maximum potential of about volts. Preferably a potentiometer 215 is employed so that conductors 216 and 213 represent a variable source of D. C. up to a maximum of about 150 volts. The two sources of D. C. are provided to impress a suitable value of D. C. current on the plates of the various tubes employed and in operating voltage responsive devices, as markers, meters, or the like.

Also, said box 211 represents a source for single phase A. C. energy along conductors 217 and 218. The source of single phase A. C. between conductors 217 and 218 is preferably isolated from the secondary of the transformer illustrated in the box 196 and hence the indication just described. The positive D. C. energy on conductor 212 is connected by conductor 219 and variable resistance 220 with the plate of tube 207. Similarly, the said D. C. positive energy from conductor 212 is connected by conductor 219 and variable resistance 221 with the plate of tube 208. The negative D. C. from conductor 213 is fed to the cathodes of the tubes 207 and 208 by conductor 222 which interconnects conductor 213 and conductor 223. Conductor 223 is connected with conductor 197 which connects to conductor 224 via variable resistance 225. Conductor 224 is connected directly to the cathodes of tubes 207 and 208. Tubes 207 and 208 employ suppressor grids 227 and 228 which are normally held at cathode voltage and the said cathodes and the said suppressor grids may be interconnected respectively by conductors 229 and 230 or internal conductors built into the tubes. The screen grids 231 and 232 are preferably held at a positive potential with respect to their respective cathodes. This may be accomplished by connecting a variable re sistance 233 between conductor 219 and conductor 234 connected to the screen grid 231 of the tube 207, and connecting a variable resistance 235 between conductor 219. and conductor 236 connected to the screen grid 232 of the tube 208. The conductor 234 is connected through a by-pass condenser 237 to conductor 222 and the conductor 236 is connected to conductor 222 through a by-pass condenser 238. Conductor 223 connects conductor 222 to conductor 197. Conductor 197 is connected to conductor 224 through variable resistance 225and by-pass condenser 226. Thus, a screen grid return is provided between the screen grids of the tubes 207 and 208 and their respective cathodes. Thus, the excitation circuit for tube 207 is from common conductor 197 to the cathode of tube 207, thence to the grid 209, thence along conductor 202 to the other source conductor 198. Similarly, the excitation circuit of tube 208 is from common conductor 197 through variable resistance 225 and by-pass condenser 226, along conductor 224, from the cathode to the grid of tube 208, thence along conductor 203 and thence through coupling condenser 204 to source conductor 199, the other source of A. C. energy.

An A. C. flow in tube 207 from the cathode to the plate thereof follows a path from the cathode to the plate, thence along conductor 239, through fixed resistance 240, along conductor 241, along conductor 242, through coupling condenser 243 to conductor 222, to conductor 223, to conductor 197, from conductor 197 through variable resistance 225 and by-pass con- 15 denser 226 to conductor 224, and thence to the cathode of the tube 207.

Similarly, the flow in tube 208 is from the cathode to the plate thereof and thence along conductor 244 through fixed resistance 245 to conductor 242. The energy flow from conductor 242 to the conductor 224 (interconnecting the two cathodes of the tubes 207 and 208) is the same as that just described in connection with tube 207 and hence is not now repeated for tube 208.

Thus, the A. C. flow in tube 207 between the cathode and the plate is in a circuit including conductor 239, and the A. C. flow between the cathode and the plate of tube 208 is in a circuit including conductor 244. Tubes 246 and 247 may be of the triode type and the plate of tube 246 is connected to conductor 239 and the plate of tube 247 is connected to the conductor 244. The energies on conductors 239 and 244- are out of phase with each other 120 as the grids 209 and 210 were charged by energy from source conductors 198 and 199 respectively. Thus, A. C. is impressed on the plates of tube 246 which is 120 out of phase with the A. C. impressed on the plate of tube 247.

By the circuits including tubes 207 and 208 and adjustable resistors, I have made provision for raising the voltage values on conductors 239 and 244 as respects their original voltages respectively on source conductors 198 and 199. Also, I have been able to maintain the same phase relation, and with selection of appropriate values to variable resistors I am able to change the voltages on conductors 239 and 244 in relatively small increments. In the apparatus of Fig. 1, the device to secure voltage increments of desired values was obtained through the variable transformer 32. Variable transformers to provide exact and relatively small increments are rather expensive and hence it is desirable to employ electronic means to provide for a desired voltage value rather than by the transformer indicated in connection with Fig. 1.

In Fig. 5, I indicated a means of providing variable voltage values on conductors 157 and 158 and at the same time to change phase relationship so that the phase relationship between conductors 157 and 158 was that they were out of phase with each other by 180. In view of the fact that I started with voltages on source conductors 198 and 199 out of phase with each other by 120 in Fig. 6, I was able through the circuit and parts shown to provide an adjustable desired voltage value on conductors 239 and 244 electronically and without the use of transformers. Thus, tubes 246 and 247 corerspond to tubes 162 and 163 of Fig. or tubes 43 and 44 of Fig. l.

The A. C. flow in tube 246 will commence with the energy on the cathode of tube 207, thence along conductor 224, through variable resistance 225 and by-pass condenser 226. along conductor 222, along conductor 248, through variable resistance 249, through a selected portion of potentiometer 250. along conductor 251, through variable resistance 252 to the cathode of tube 246, to the plate of tube 246, along conductor 239 to the plate of tube 207. Thus, the tube 246 is in parallel with tube 207. Any change of ilO-W in the tube 207 will be reflected in the flow in tube 246.

Similarily. the tube 247 is in parallel with tube 208. The circuit may be traced commencing with the cathode of tube and along conductor 224. In connection with tube 246, it was just pointed out that energy from conductor .24 passes to potentiometer 250. This occurs in connection with the A. C. low in tube 24 Thence energy from potentiometer 250 passes via conductor 253 to the cathode of tube 247, thence from the cathode to the plate of tube 247, thence along conductor 244 and to the plate or tube 208.

In Fig. .l of the drawings I provide means to adjust the phase of the energy leading to the grids 63 and 64 of the tubes so the same could be initially adjusted to be out of phase with the energy impressed on plates 55 as well as the energy impressed on plates 57. In said figure it was necessary to provide for an initial adjustment and with the optimum adjustment of so as to produce maximum difference of flow in tubes 43 and 44 with changes in flow due to the shift of phase brought about by reason of material between the plates of material condenser 75.

Similarly, in Fig. 5 of the drawings, the phase relation ship of the energy to the grid of tube 175 was adjusted relative to voltage from the conductor 188 so that the resulting phase relation of the energy on conductor 189 would be in a circuit including the material condenser 75 so that the phase relation of the energy on the grids of tubes 162 and 163 relative to the plate cathode voltages of said tubes was such so there would be maximum differential by changes in the material condenser 75.

In Fig. 6 of the drawings I start with three-phase and with the phase relation of between phases. How ever, this phase relationship does not maintain itself and there is usually a shifting of phase due to the characteristics of the various electronic devices employed. Tubes 246 and 247 function similarly to tubes 162 and 163 of Fig. 5 and tubes 43 and 44 of Fig. 1. Due to the various devices necessary in an electronic circuit, the conductive and capacitative reactions tend to change the phase and distort wave form and thus it I attempted merely to use source conductor 200 to feed the grids of tubes 246 and 247 it would not be practical .to adjust the phase of the grid of the tube 246 relative the cathode and plate voltages thereof and at the same time make a similar adjustment relative the grid of tube 247. Thus, in order to get proper sensitivity upon change of capacity and conduction in the material condenser 75, it is necessary to provide for a justing of the phase of the grid circuit even though We initially started with 120 out of phase of the source conductor 200 as respects each of the source conductors 198 and 199.

The grid circuit of the tubes 246 and 247 may be traced commencing from source conductor 200 through coupling condenser 254 to conductor 255. A plurality of condensers 256, each having different values, are disposed in parallel and connected with conductor 255. A plurality of variable resistances 257, each having a different value, are provided in parallel and connected with conductor 258. A movable contactor arm, comprising independently movable portions 259 and 260, bridges between any one of the variable resistances 257 and any one of the condensers 256. The conductor 258 is connected by a conductor 261, having a coupling condenser 262 disposed therein, with the common source conductor 197. The output conductor 263 thus has impressed thereon the desired phase shift as respects the voltage impressed on the plates of tube 246 and tube 247. Thus, by any change in the material condenser 75, the flow in one tube may rise while the how in the other tube may fall and thus we have a maximum signal between the cathodes of tubes 246 and 247. v

In order to amplify the signal on conductor 263 (without employing a resonant circuit or a transformer) and at the same time maintain the phase relation of the voltage thereon, conductor 263 connects with a potentiometer 264 and in turn with the grid 265 of pentode 266.

The plate 267 of tube 266 is energized with positive D. C. from conductor 212. This may be accomplished by disposing inductance 268 between conductors 212 and 269. Also, filter condensers 270 and 271 are disposed between positive and negative source conductors 212 and 213. Conductor 269 connects with variable resistance 272 which in turn connects with the plate 267 of tube 266. The screen gnid 273 of tube 266 is preferably maintained at a desired positive potential. This may be accomplished by a conductor 274 having disposed therein a variable resistance 275 and a conductor 276 disposed between the screen grid 273 and the conductor 274. The screen grid 273 is connected to the negative conductor 213 via by-pass condenser 2'74, disposed between conductor 2'76 and conductor 213.

A suppressor grid 277 is preferably maintained at cathode voltage and this may be accomplished by a conductor 278 disposed between the grid supress'o-r 277 and the cathode of the tube 266. While I have shown an external connection by means of conductor 278, obviously an internal connector may be employed as indicated in connection with .tubes 207 and 208 and thus such connection may be built into the tube at the time of its manufacture, V

The ne ative voltage on the cathode of tube 268 commences with negative source ccnductor2fl3 through variable resistance to the cathode of tube 266.

The A. C. flow in tube 266 starts with source conductor 197, along conductor 223, along conductor 222,

along conductor 213, through by-pass condenser 280 and variable resistor 279, from the cathode of tube 266 to the plate 267 thereof, along conductor 281, through coupling and limiting condenser 282, through material condenser 75 (the materialcondenser 75 may be the same in all forms of my invention and will be more described in detail with subsequent figures), through coupling condenser 76 and thence via conductor 283 to the grids of tubes 246 and 247. The grid return from tubes 246 and 247 passes via conductor 284 to potentiometer 285, along conductor 286 through condenser 243, along conductor 222, along conductor 248, through variable resistor 249, through potentiometer 250, and thence to the common conductor 251-253 interconnecting the cathode of tubes 246 and 247.

Potentiometer 285 and a source of D. C. supply 287 provide suitable grid bias to the tubes 246 and 247. The grid bias provided by potentiometer 285 and battery 287 for tubes 246 and 247 provides for suitable control of the wave form in the circuit including therein material condenser 75. As indicated in Fig. 7 of the drawings we have a square top shaped Wave rather than a pure sine wave similar to the Waves indicated in Figs. 2, 3 and 4 of the drawings. By having a square top shaped wave the response signal between the plates of material condenser 75 tends to follow a rectilinear curve rather than an arcuate curve and hence the response signal tends to more accurately follow value changes in the conductance and capacity reactions of material disposed between the plates of material condenser 75.

Due to the fact that I may adjust the phase relation of the voltage on the grids of tubes 246 and 247 relative to the cathode plate voltage of tube 246 and the cathode plate voltage of tube 247, the flow in one of said tubes rises with changes of phase shift in the grid voltage relative to the other. Thus, again there will be a potential difference between conductors 288 and 289 connected respectively to the cathodes of tubes 246 and 247. Such changes in flow are indicated in Fig. 7 of the drawings.

1 have indicated an illustrative circuit and apparatus for utilizing the difference in potential between conductors 288 and 289. Conductor 288 is coupled with inductor 290 which functions similarly to inductor 113 of Fig. 1. Inductor 290 is coupled with a latch relay 291 which is similar to latch relay 111 of Fig. 1. Latch relay 291 includes a relay coil 292 which is similar to relay coil. 114 of Fig. l. Inductor 290 is coupled with conductor 293 which is coupled with the relay coil 292. Relay coil 292 is also coupled with conductor 294 which in turn is connected with conductor 289 which in turn is connected with the cathode of tube 247. Also, energy from inductor 290 may pass to either one of two variable resistances 295 which are connected with conductor 289. The variable resistances 295 have a similar function to the variable resistances 118 of Fig; 1. Also, the conductor 288 is coupled to the conductor 289 through condenser 296. Thus, similar to Fig. l the switch mechanism of latch relay 291 may be caused to close (similar to latch relay 111) when a signal of predetermined strength obtains between conductors 288 and 289 which ftmction similarly to conductors and 81.

Again, latch relay 291 is provided with a solenoid switch mechanism 297 which functions similar to the solenoid mechanism 103 of Fig. 1 to provide for time control of the switch mechanism of latch relay 291. Whenever the switch mechanism of latch relay 291 is closed energy will commence from source conductor 216 through the coil of relay 298, along conductor 299, through the then closed switch mechanism of latch relay 291, along conductor 300 to the opposite source conductor 213. Upon closing of the switch mechanism of relay 298, energy passes from A. C. source conductor 218 to conductor 301 through the then closed switch mechanism of relay 298 along conductor 302 to the coil of relay 303-relay 303 corresponds to relay 97 of Fig. 1. Energy passes from the coil of relay 303 to conductor 304 and thence to the other source of single phase A. C. 217. Thus, an isolated circuit is controlled by relay 303 whenever the switch mechanism of latch relay 291 and the switch mechanism of relay 298 are closed. This is similar to the operation of relay 97 of Fig. 1. The various circuits and mechanisms connected between conductors 288 and 289 of Fig. 6 are similar to those connected between conductors 80 and 79 of Fig. 1 except a combination of devices employing single phase A. C. and D. C. are indicated in connection with Fig. 6 of the drawings. Functionally, however, the apparatus and circuits are the same.

Whenever the coil of relay 303 is energized the switch mechanism thereof is closed and a circuit is established between conductor 305 connected to source conductor 218 and conductor 306 connected with solenoid 307 (similar to solenoid 132 of Fig. 1), and thence along conductor 308 to the other, source conductor 217. Energizing of solenoid 307 operates marker mechanism 309 (similar to marker mechanism 107 of Fig. 1) so that the marking portion 310 provides a suitable mark. Operation of marker mechanism 309 closes the switch mechanism disposed between source conductor 218 and conductor 312'1. Thus, a circuit is energized from source conductor 218, through the closed switch mechanism of marker mechanism 309, along conductor 311, through the coil of relay 312, along conductor 313, through the coil of solenoid 297, along conductor 314 to the other source conductor 218.

Relay 312 corresponds to relay 120 of Fig. 1 and thus the closing of the switch mechanism of relay 312 causes two circuits which may be briefly described as follows: A holding circuit comprises conductor 311, conductor 315, the top switch blade of relay 312, conductor 316 to conductor 218. The other circuit includes conductors 317, 318, and the lower switch mechanism of relay 312 which parts correspond to conductors 124 and 123 and the lower switch mechanism of relay 120 of Fig. 1. Conductors 304 and 218 represent a source of energy for the timer integrator 319 and such parts correspond to conductors 125, 126 and timer integrator of Fig. 1. Relay 320 corresponds to relay 101 of Fig. l and its switch points are normally closed. When its said switch points are closed energy flows from source conductor 217, along conductor 304, along conductor 321 through the normally closed switch points of relay 320, along conductor 322, along conductor 313 through solenoid coil 297, along conductor 314, to the other source of energy 218. Thus, normally solenoid 297 controls the switch mechanism of latch relay 291 and the switch mechanism thereof cannot be closed until relay 320 operates to open its switch mechanism. As indicated in connection with Fig. 1, relay 320 has its switch mechanism open for predetermined periods, the time period thereof starting with the time of the last operation of the marker mechanism which marking mechanism closes its switch mechanism each time it operates.

In connection with Fig. 6 of the drawings I show voltage r onsive devices operated by an impulse or differential in volt e between conductors 2% and 239. Obviously, st. able instruments may be employed to indicate tl e value of such signal and calibrated directly in moisture values. Also, electronic means may be caused to operate by a voltage change between electrodes 23-3 and 239 and which electronic means would include therein vacuum tubes or thyratrons. If circuits including vacuum tubes are employed therein the signal can be amplified or otherwise utilized. If a circuit is established between said electrodes 28% and 239 and said circuit means include therein a thyratron, then the thyratron would fire or cause flow therein and responsive devices may be connected with said thyratron. This applies to conductors 8% and 8 of Fig. 1 and conductors 171 and ll72 of Fig. 5.

Referring to Fig. l of the drawings, the combination of resistors 45, as, and in the cathode and in turn the grid return circuits is designed to provide the desired difference in potential between the grids 6364- and the cathodes S d-51 of the tubes 4-35 and However, the signal strength to the grids 63 and 6d will vary With the capacity of the condenser '75. The capacity and in turn the signal from the condenser 75 will vary with difierent installations and hence a capacity may obtain when ma terial is not passing through the condenser 75, which will overload the tubes 43 and 44 or one thereof, it conventional and commercially available tubes are employed. Thus, it may be desired under some circumstances, where the capacity Of condenser 75 is rather high and there is a relatively high null signal, to modify the circuit of Fig. 1.

Now referring more specifically to Fig. 21 of the drawings, I have shown an application of my invention where a single tube is employed rather than two tubes. In such 2l, all parts similar in function to those illustrated in l are given the same numbers and thus need not be described in detail. Primarily I have eliminated the tube 44 and parts associated therewith. In addition I have provided a conductor 345 connecting the condenser 75 with the conductor 73, which in turn is connected with the grid 63 of the tube l3. Also, I have provided a conductor 346 connecting conductor 47 with a source of potential, such as a battery 347. A variable resistor is connected in the circuit between the battery 347 and the conductor 78 which connects with the grid 63 of the tube 43.

In various installations, the value of the condenser 75 with no material passing therebetween, will vary with the job for the best results. Thus, when. a given value is selected for the condenser 75 for a particular job, the potential of battery 34-7 and the resistance of variable resistor 3455 can be selected so that the null or no material signal of condenser 75 is such that the desired difference in potential exists between the cathode means 55) and the grid means 63 of the tube 43. Under such circumstances. then the presence of material between the plates of the condenser 75 will be such as to provide a. signal which will cause the proper phase shift so that a desired signal. which will operate voltage responsive devices, will obtain between the conductors 8t) and 81.

Thus, in Fig. ll of the drawings 1 have provided a device which is responsive to variable electrical conductances and capaci'tances between the plates of condenser 75. Also, in said circuit I have provided an electronic tube means 4-3 providing cathode means 53, grid means 63, and plate means 55. The conductor 47 and the resistance and a portion of the resistance 25 connects the cathode means Stir with one source of alternating current by way of the conductor 53. The voltage responsive device is connected between conductors 80 and 81 and the conductor is connected with the cathode means The conductor 31 is connected through variable re- 45, through variable resistor 43, along conductor 4-7, and thence along conductor 53 to the originally mentioned conductor of a source of alternating current. Next, the grid circuit includes therein the conductance and capacity of the material under test between the plates of the condenser 75. Also, the said circuit including the conductance and the capacity of the material under test is connected with a conductor '78 which has imprcsse thereon a voltage as respects the conductors 53 and 47 which is accomplished by conductor 346 which leads through a battery 347 and through a variable resistor 348 and is then connected to the conductor '78. Obviously the battery 34% is merely illustrative of a source of E. M. F. and is to be considered as such rather than a limitation. In the circuit of tube 43, there is a plate circuit which includes the plate means 55 of said tube which is connected with a conductor 5'6 which has a voltage asrespects the first 1 entioned conductor 53 leading to a source of alternating current. Under the circuit just described variations in the conductance and capacity of the material under test between the plates of condenser '75 will be reilccte in the voltage responsive devices coupled between the conductors 3t) and 31.

Referring now to Figs. 7 and 8 of the drawings, the curve 323 represents the applied A. C. voltage in the cathode-plate system of tube 246, the curve 324 represents the applied A. C. voltage in the cathode-plate system of tube 247, and curve 325 represents the applied A. C. voltage to the grids of tubes 24-6 and 247. The phase of the voltage represented by curve 323 lags and is out of phase with the voltage represented by the curve 324 by The voltage represented by the curve 325 leads the VOliIEWfi represented by the curve 324- by 120. Under such operating conditions the broken line curve 326 is illustrative of the flow from the cathode to the plate of tube 2%, and curve 327 is illustrative of the flow in tube In the event of shift of phase of the A. C. applied voltage to the grids of 246 and 24-7 by reason of the conductance and capacity reaction due to materials present between the plates of material condenser 75, the phase may be shifted of the voltage applied to the grids of said tubes 246 and 2417. The amount of such shift is represented in Fig. 5 as being 120 and thus the voltage curves 32.5 and 323 are in phase while the volta e curve 324 is still 120 out of phase with them. Under such circum stances the curve 323 will represent the dew in tube 246 while the curve 329 will represent the flow in tube 7247. Again the curves of Figs. 7 and 8 are like those of Figs. 2 to 4 and they are to be considered illustrative and not to represent actual valuesor exact wave forms. However, the curves very clearly illustrate the fact that a phase shift of the applied. A. C. voltage in the grid circuits of the two tubes 246 and 247, while the applied A. C. voltage on the cathode-plate systems of the tubes remain out of phase with each other, will cause a change in flow and thus provide a signal between conductors 288 and 289 which can be utilized in many ways.

Referring now to Fig. 9 of the drawings, the impulse between conductors 79 and 89 (Fig. l), conductors 171 and 177. (Fig. 5), or conductors 238 and 289 (Fig. 6) may be utilized in various ways. In Figs. 9 to 13 in elusive, the lead-in wires for such signals are designated as conductors 77 and 79 and the condenser between the operative mechanisms connected with said conductors is designated as the material condenser 75.

Referring now to Fig. 9 of the drawings, the conductor 79 may be connected to a roll disjfos above and in contact with traveling wood stool; Also, the conductor 77 may be connected with roll 332 disposed below and in contact with the trz'rveling wood stock 331. In connection with Fig. 9 it is to be remembered that 331 is not to be limited to traveling wood stock and that material 331 is merely representative of material. containing therein moisture content which is to be determined or which is to cause a voltage response 

